Three-dimensional optical data storage in fluorescent dye-doped photopolymer

Abstract

A host matrix—normally a binder such as cellulose acetate propionate in a solvent such as acetone—contains a radiation-polymerizable photopolymer—normally a monomer like dipentaerythritol pentaacrylate in combination with a crosslinker like 1-vinyl-2-pyrrolidinone, an initiator like N-phenyl glycine, and / or a photosensitizer like camphor quinone—that is initially uniformly doped with a stable dye—typically Rhodamine B and / or Bodipy Red—that photoinitiates photopolymerization. Upon selective exposure of certain regions of the matrix by radiation, most normally laser light radiation, the dye will initially migrate and redistribute itself to radiatively-exposed regions until, dye migration being substantially complete, photopolymerization will occur, locking the migrated dye in place at a relatively higher concentration at the selectively exposed regions. The dye therein stably located can be optically detected by, preferably, light-radiation-stimulated fluorescence. The medium thus serves as an optical memory, including of the volume type, that can be reliably permanently written quickly and inexpensively at high density.

Description

REFERENCE TO RELATED PATENT APPLICATIONS[0001]The present patent application is related to, and claims priority from, U.S. provisional patent application Ser. No. 60 / 129,989 filed Apr. 12, 1999, for THREE-DIMENSIONAL OPTICAL MEMORY IN FLUORESCENT DYE-DOPED PHOTOPOLYMER to the selfsame inventors as is the present application. The present application is related to U.S. patent application Ser. No. 09 / 547,396, now U.S. Pat. No. 6,501,571 filed on an even date for THREE-DIMENSIONAL HOLOGRAPHIC STAMPING OF MULTI-LAYER BIT-ORIENTED NON-LINEAR OPTICAL MEDIA, also to the same inventors. The content of the related patent application is incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention generally concerns optical data storage, optical memories, polymers, multi-layer optical storage, and volume, or 3-D, optical data storage.[0004]The present invention particularly concerns the radiation writing of monolithic multi-layer optical...

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Benefits of technology

[0012]In comparison to the prior art, where changes in volume media have previously been photochemically induced, the present invention offers several advantages. First, molecules within the pre-polymerized, un-exposed, optical medium exhibit such high diffusion and mobility as is, at the initiation of the process, desirable. This high mobility—as opposed to, for example, a solid—makes that constituent components of the volume media can “move around”. In the prior art this has been useful so that the components can undergo photo-induced chemical reaction, or photochemistry. In the present invention the mobility is more concerned with the movement of a photo-detectable material, i.e., a dye.

[0014]However, in the present invention this initial mobility will cease. Initially the dye molecules are drawn to regions of exposure, depleting surrounding regions and increasing contrast. However, over a short period the radiation (light) exposure will cause such spreading polymerization as ultimately locks all constituent components into the positions by then assumed.

[0015]This is an essential characteristic, and forte, of the media of the present invention: mobility followed by immobility. After such minor lapse of time as permits all chemicals and photochemicals to “move into place” (over molecular dimensions), everything “locks up” and nothing is free to move, essentially forever. This is very beneficial. Effectively nothing changes in a memory once written. The dye can “bleach out” slightly after prolonged exposure to bright light, and / or over millions of radiation interrogations, but is essentially stable, and maintaining of a bright fluorescing capability indefinitely long. The exposed and polymerized radiation memory is essentially just as stable as present (circa 2000) memories of both optical and magnetic types that it serves to replace.1. A Radiation Recordable Medium

Problems solved by technology

However, despite the current search for shorter wavelength lasers and more efficient coding techniques, standard planar optical storage technologies may not be able to keep up with the ever-increasing demand for faster data rate, higher capacity, media.

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